It has been shown that, for time-harmonic electromagnetic fields with exp (-i.omega.t) excitation, a homogeneous, low loss, isotropic chiral (optically active) medium can be described electromagnetically by the following constitutive relations: EQU D=.epsilon.E+i.xi..sub.c B (1) EQU H=i.xi..sub.c E+(1/.mu.)B (2)
where E, B, D and H are electromagnetic field vectors and .epsilon., .mu., .xi..sub.c represent the dielectric constant, permeability and chirality admittance of the chiral medium, respectively. A "chiral medium" comprises chiral objects of the same handedness, randomly oriented and uniformly distributed. The chirality admittance .xi..sub.c is a measure of handedness of the medium. A chiral object is a three-dimensional body that cannot be brought into congruence with its mirror image by translation and rotation. Therefore, all chiral objects can be classified in terms of their "handedness." The term "handedness," as known by those with skill in the art, refers to whether a chiral object is "right-handed" or "left-handed." That is, if a chiral object is right-handed (left-handed), its mirror image is left-handed (right-handed). Therefore, the mirror image of a chiral object is its enantiomorph.
Chiral media exhibit electromagnetic chirality which embraces optical activity and circular dichroism. Optical activity refers to the rotation of the plane of polarization of optical waves by a medium while circular dichroism indicates a change in the polarization ellipticity of optical waves by a medium. There exists a variety of materials that exhibit optical activity. For example, for 0.63-.mu.m wavelength, TeO.sub.2 exhibits optical activity with a chirality admittance magnitude of 3.83.times.10.sup.-7 mho. This results in a rotation of the plane of polarization of 87.degree. per mm. These phenomena, known since the mid nineteenth century, are due to the presence of the two unequal characteristic wavenumbers corresponding to two circularly polarized eigenmodes with opposite handedness. The fundamentals of electromagnetic chirality have been treated in books by Kong [J. A. Kong, Theory of Electromagnetic Waves, 1975] and Post [E. J. Post, Formal Structure of Electromagnetics, 1962]. More recent work includes the macroscopic treatment of electromagnetic waves with chiral structures [D. L. Jaggard et al. Applied Physics, 18, 211, 1979], the analysis of dyadic Green's functions and dipole radiation in chiral media [S. Bassiri et al. Alta Frequenza, 2, 83, 1986; N. Engheta et al. IEEE Trans. on Ant. & Propag., 37, 4, 1989], and the reflection and refraction of waves at a dielectric-chiral interface [S. Bassiri et al. J. Opt. Soc. Am. A5, 1450, 1988].